After harvesting soybean fields, it's time to go back out and sample for soybean cyst nematode, say experts at the Ohio State University. They recommend sampling in the fall – because in most cases this is what the population will be in the spring. Warmer weather this year should offer ample time to collect and process the samples in plenty of time for spring planting.
Levels of SCN and concerns
If your SCN report in the past has come back as:
Not detected: this is not surprising. Remember that SCN sits in pockets and can be quite variable. Continue to monitor your fields.
Trace: May begin to measure some yield loss on susceptible varieties, especially on lighter soils.
Low: Plant SCN-resistant soybean varieties or rotate to a non-host crop (corn or wheat).
Moderate: Rotate to a non-host crop and follow with SCN-resistant varieties the following year. We have planted susceptible varieties in fields with this level of SCN and have recorded 20-50% yield loss.
High: Rotate to a non-host crop for two to three years, then sample for SCN to determine if populations have declined to a level where soybeans can be planted again.
SCN is picky about what it feeds and reproduces on but it does like a few weed hosts and cover crops as well as soybean. If you have SCN in your fields, it is important to also control winter annuals such as purple deadnettle, but also avoid cover crops such as several of the clovers, cowpea and common and hairy vetch.
Processing of samples does cost time and money, so here are a few thoughts on how to sample or how to target your sampling to get the best information for your money. Through funds from the soybean check-off, OSU has completed several targeted surveys over the past 5 years. The research group tended to target soybean fields where yields were stuck or below 30 bushels/acre. Or pockets in the field where the soybeans tended to be shorter or where they matured earlier and always yielded less than the rest of the field. SCN was detected in almost all of these situations, so these are the ones that should have the top priority for sampling.